It's springtime, and Republicans are feeling hawkish again. See how Sen. Rand Paul's views on foreign policy have shifted as he's adopted a more aggressive stance. It wasn't that long ago when the Kentucky Republican was staging a talking filibuster against the Obama administration's drone policy, warning the American people that the president might deploy a drone against an American citizen on American soil without judicial process.

At the time, the administration criticized Paul for engaging in "wild hypotheticals" before agreeing that using a drone to kill an American this way would be beyond President Obama's authority. Yet over the weekend, Sen. Lindsey Graham seemed to suggest that what Paul imagined as a dystopian nightmare could be a reality if the Republican from South Carolina were president.

"If I’m president of the United States and you’re thinking about joining al-Qaeda or ISIL [Islamic State], I’m not gonna call a judge," Graham said. "I’m gonna call a drone and we will kill you."

Many expect Graham to run for president. He said again Monday morning that he would announce his decision June 1.

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What's in Wonkbook: 1) Republicans meet in Iowa 2) Opinions, including Luce and Sargent on Iraq 3) The appeal of the flat tax, and more.

1. Top story: Republicans speak at Lincoln Dinner

Here's what the Republicans said Saturday night in Des Moines, as it happened. "Nearly a dozen presidential contenders or likely contenders showed up to Iowa Republican Party's Lincoln Dinner on Saturday night to pitch themselves and their ideas. ... Guests were greeted by a Abraham Lincoln impersonator." Jenna Johnson and Philip Rucker in The Washington Post.

Only Paul criticized former Florida governor Jeb Bush for his comments on Iraq. "Bush, of course, has spent the week backpedaling after initially telling Megyn Kelly in a Fox News interview that he would have authorized military force in Iraq even 'knowing what we know now'; four days after the interview aired, Bush acknowledged that he would not, in hindsight, have made the same call as his brother did. ... Taking the stage 10 minutes after Paul, Lindsey Graham went out of his way to defend Bush, blaming the unraveling of stability in Iraq on President Barack Obama, not George W. Bush." Eli Stokols at Politico.

Is the primary going to be a problem for Republicans? "Party officials are growing worried about a wide-open nominating contest likely to feature a historically large and diverse field. ... With no clear front-runner and Bush so far unable to consolidate his path to the nomination — his fumbles over the Iraq war and his brother’s legacy further exposed his vulnerabilities — the GOP’s internecine battle could stretch well into the spring of 2016. This could cost presidential aspirants tens of millions of dollars; pull them far to the right ideologically, from hot-button social issues to foreign policy; and jeopardize their general-election chances." Philip Rucker and Jenna Johnson in The Washington Post.

2. Top opinions 

SUMMERS: Forgive Ukraine's debt. "Ultimately Ukraine’s viability depends on what happens to its debts. ... When a country’s debts are so large, and its economic prospects so poor, that there is no realistic prospect of its debt being paid back in full, it is accepted that debt reduction is appropriate as a matter of burden sharing and as a way to reduce the effect of overhanging debt on growth. Things become clearer in cases when debt reduction would not be a source of systemic risk to the global financial system or license widespread defaults." The Washington Post.

LUCE: The war in Iraq has changed politics permanently. "Much like the role Vietnam played in American politics long after US choppers had flown Saigon, the Iraq syndrome stalks foreign policy debate. The latest victim is Jeb Bush, who last week gave four different answers to whether he would have emulated his brother had he known then what he knows now. ... Iraq is a mistake that will affect US politics for a generation. ... The instinct in both US parties is to avoid extravagant promises regarding the Middle East. There is little electoral appetite for foreign adventurism. Nobody is credibly arguing America can transform the Arab world into a garden of democracy." The Financial Times.

SARGENT: Bush should have known then what we know now about Iraq. "He has now flatly stated that he would not have gone to war in Iraq, as his brother did, if he’d known that the intelligence was wrong about the threat Iraq posed... The basic premise that this challenge to Jeb reinforces is that the Iraq War happened only because of bad intelligence. George W. Bush was misled by intelligence failures, and it still gives him a “sickening feeling.” In this framing, the question becomes: Will you admit that you were misled into supporting a war that everyone now agrees in hindsight was an unnecessary and tragic mistake? But this leaves out a big part of the story of the run-up to the war, which is that some people were arguing at the time against invading Iraq, on the grounds that the evidence was all right there in plain sight that Iraq did not pose a threat imminent enough to justify an invasion." The Washington Post.

BOUIE: Research suggests that segregated neighborhoods result from homeowners' racism. "It’s easy to conclude that white preference for white neighborhoods is a kind of class discrimination, which we can fix through active, interventionist policy. But in this situation, the answer we might want isn’t the one that’s true. For white homebuyers, race matters, and not just as a proxy for class. ... If this preference is a proxy for class—if whites don’t oppose black neighbors, just the conditions of black neighborhoods—then integration becomes an easier task: Improve mixed-race and predominantly black neighborhoods—enhancing schools and services—and you attract white buyers, increasing diversity and breaking down our walls of separation. But to a good degree, this preference is prejudice—a function of anti-black stigma. In which case greater integration—and greater racial equality—is even further away than it looks." Slate.

Passenger rail has always required public subsidies, even before Amtrak, notes Stanford University historian Richard White. "Amtrak is a public-private corporation, but the government’s involvement in rail began long before Amtrak. It has taken various forms: public subsidies, public stock subscriptions, the leasing of convict labor, partial public ownership of private railroad corporations, and regulation. Government funds were the lifeblood of many 19th-century American railroads. ... Railroads lost money by carrying people, but they could not simply cease to run passenger trains. Both their charters and laws required them to do so. Amtrak, which was started in 1971, was a blessing to them. They could keep the lucrative freight and ditch the costly passengers." The New York Times.

Putting solar panels on roofs is inefficient, writes utility lawyer Brian H. Potts. "The rooftop-solar craze is wasting billions of dollars a year that could be spent on greener initiatives. It also is hindering the growth of much more cost-effective renewable sources of power. ... Utilities are forced by law to purchase solar power generated from the rooftops of homeowners and businesses at two to three times more than it would cost to buy solar power from large, independently run solar plants. Without subsidies, rooftop solar isn't close to cost-effective. ... Large, utility-scale solar power plants can cost as little as five cents (or six cents without a subsidy) per kilowatt-hour to build and operate in the sunny Southwest. These plants are competitive with similarly sized fossil-fueled power plants. But this efficiency is possible only if solar plants are large and located in sunny parts of the country." The Wall Street Journal.

3. In case you missed it

Sen. Mitch McConnell (R-Ky.) does not want to compromise on the National Security Agency. This is the "last legislative week before key provisions that authorize some of the government's sweeping domestic surveillance powers are due to lapse at the end of the month. ... McConnell's strategy, observers say, is familiar: Run out the clock until lawmakers sympathetic to reining in the post-9/11 surveillance muscle of the Patriot Act buckle under fears that a complete expiration could jeopardize national security. But the leaks of Edward Snowden that began nearly two years ago—which included the exposure of the phone-records program—have changed the climate in Congress. Several senators, in addition to House leaders, have stated that they have no interest in an extension of any length to the Patriot Act's spy programs that don't include substantial reform. And both Sen. Rand Paul and Sen. Ron Wyden have said they will filibuster any 'clean' reauthorization attempt." Dustin Volz in National Journal.

Obama will restrict transfers of military equipment to local police. "Mr. Obama is taking the action after a task force he created in January decided that police departments should be barred from using federal funds to acquire items that include tracked armored vehicles, the highest-caliber firearms and ammunition, and camouflage uniforms. The ban is part of a series of steps the president has made to try to build trust between law enforcement organizations and the citizens they are charged with protecting. Mr. Obama planned to promote the effort on Monday during a visit to Camden, N.J. The city, racked by poverty and crime, has become a national model for better relations between the police and citizens after replacing its beleaguered police force with a county-run system that prioritizes community ties." Julie Hirschfeld Davis in The New York Times.

Federal sentencing reform is now a possibility, as one crucial opponent is ready to compromise. "The future of the movement is in the hands of one man—Senate Judiciary Committee Chairman Chuck Grassley, who is in the middle of what may be a real effort to move forward. And while staff discussions are just beginning, what just a few months ago seemed highly unlikely is beginning to seem possible. ... Grassley says he is most interested in cobbling together new legislation—at least on sentencing reform—to be voted on in committee. That way, the once-reluctant change agent could carefully ensure that reductions to sentencing are not made across the board." Lauren Fox in National Journal.

Republican presidential candidates are rallying around a flat tax. "So far, at least four Republicans have talked up their support for a flat tax, or a single rate for everyone, which would replace the current system, which taxes richer people at a higher rate on ordinary income than less affluent taxpayers. ... Supporters say a flat tax will unleash a torrent of economic activity, particularly if the tax is set at a relatively low rate between 10 percent and 20 percent for individuals and businesses and exempts all investment income, as most of the plans do. But even if economic activity flourished, lowering taxes on the rich means less affluent taxpayers would end up paying more of the overall tax burden. ... Even rosy projections about growth and promised spending cuts show that most flat-tax proposals, by setting the rate low enough that it doesn't look forbidding to ordinary taxpayers, generate too little money to prevent the budget deficit from increasing substantially, undermining another key promise of Republican candidates." Patricia Cohen in The New York Times.