Senate Minority Leader Mitch McConnell (R-KY) delivers remarks during the second day of CPAC. (Alex Wong/Getty Images) Senate Minority Leader Mitch McConnell (R-Ky.) delivers remarks during the second day of Conservative Political Action Conference. (Alex Wong/Getty Images)

The Post reports that one Senate forecasting model puts the Republicans’ chances of winning the Senate at 54 percent. The choice of which states will make up that winning margin is odd. (Iowa, really?) The Arkansas seat is not one of the six seats needed to win, according to this model, although the authors concede this may be wrong. So much for models.

If, however, you look at history, the GOP has some reason for optimism. Larry Sabato points out, “In a large majority of cases, the president’s party does poorly in midterms, especially the second midterm of a two-term administration. It’s a rare president who doesn’t make enough mistakes by his sixth year to generate a disproportionate turnout among his opponents — thus producing a political correction at the polls. Presidents Dwight Eisenhower in 1958, Lyndon Johnson in 1966, Richard Nixon/Gerald Ford in 1974, Ronald Reagan in 1986 and George W. Bush in 2006 all experienced significant corrections in their sixth-year elections.”

If you go back to the last three second-term midterms, the party holding the White House had losses of six in 2006; zero in 1998 (thanks most likely to the Clinton impeachment), and eight in 1986. If you count Gerald Ford’s tenure as in essence the remainder of Richard Nixon’s term, you get five losses in 1974.

Sure, history repeats until it doesn’t, but there are reasons why Republicans are especially excited this year. For one thing, election races in red states (i.e. states that voted for Mitt Romney in 2012) are enough, in and of themselves, to put the GOP over the top (Alaska, Arkansas, Louisiana, West Virginia, Montana, South Dakota and North Carolina.)

And, most important, there are nationalizing issues that would, if they continue or further tilt in the Republicans’ direction, set the stage for a surge year. In 2006, there was the war and Katrina, plus a series of House Republican scandals. In 1994, Newt Gingrich helped create his own wave with the Contract for America, pulling in a majority with a unified message.

The unifying themes for Republicans, of course, begin with Obamacare. Each of the incumbents who voted for it can be accused accurately of being a decisive vote. The law is a mess (hence the constant unilateral fiddling) and unpopular; yet Senate Democrats have stood by the president, adamantly refusing to repeal, delay or fix it. Indeed, Obama is generally unpopular (to a greater extent in the red states with Senate races), so tying every Senate candidate to Obama’s policies and rhetoric (Disincentives to work are good! You can keep your insurance!) is a good strategy.

If Republican Senate candidates are smart, they also will being using the raft of popular legislation passed through the House that Senate Majority Leader Harry Reid (D-Nev.) refuses to take up. Arguably, with a GOP Senate, there would be a whole bunch of pro-growth, pro-jobs legislation landing on the president’s desk.

Another issue may be the Obama administration scandals (e.g. the Internal Revenue Service), dereliction (ludicrously unqualified nominees), overreach (changing immigration law) and stonewalls (Benghazi, Fast & Furious, etc.). Senate Dems have taken no interest in crossing the White House on these issues. The Senate hasn’t fulfilled its institutional role of oversight, allowing the president to run amok with executive powers. (If Republicans overplay this, though, they risk turning off voters and painting a picture of nonstop conflict in the last two years of the administration.) This should include the president’s mishandling of foreign policy, the potential for a phony deal with Iran (the interim deal is secret; will we even see what is in it?) and appointment of buffoonish cabinet members (e.g. Chuck Hagel), whom the Democrats backed without question.

Before Sen. Mitch McConnell (R-Ky.) — and yes he’s nearly certain to win the primary and very likely to consolidate support and win reelection — starts measuring the drapes in the majority leader’s office, however, Republicans should keep in mind four easy ways to lose their chance at the majority. First, if the GOP picks wacky, unvetted candidates who emulate the faction of the GOP voters dislike the most, voters may be compelled to go with the flawed but familiar Democratic incumbents. Second, providing no alternative to Obamacare leaves Republicans vulnerable to the charge they will “take away” insurance from millions. Third, further antics that seek to paralyze the Senate and/or stop generally popular provisions from going through will give voters pause about turning the Senate over to them. And fourth, Republicans better be ready for mean, negative campaigns and phony issues like the “war on women.” (Actually women are doing comparatively well these days.)

When you go through it all, Republicans have a darn good chance to take the Senate, based on an array of factors. But they thought so in 2010 and 2012.