Senate Republicans pitched a curveball Tuesday into their tax debate: They're going to try to undo a key part of Obamacare at the same time.

Republicans announced Tuesday that their tax plan will include an attempt to repeal Obamacare's individual mandate, which forces most Americans who don't have health care to pay a fine.

The news was a surprise to most tax watchers. But it is ambitious. And a potential political risk. It injects one of the most politically precarious issues for Republicans (repealing parts of Obamacare) smack into another politically precarious issue (tax reform).

“It's hard to see how this does anything but greatly complicate the tax bill's chances of being enacted,” said Stan Collender, a budget expert who writes for

Senate Republican leaders see it differently, apparently. Here are pros and cons for Senate Republicans if they move forward with trying to undo Obamacare's individual mandate in their tax bill.

Pro: If successful, they will have knocked out two birds with one vote.

They'd be undoing a major part of Obamacare and rewriting the tax code. Those are two major wins that so far have eluded Republicans, who control all of Washington right now.

House Republicans have voted repeatedly to undo the individual mandate, so this likely would not be controversial on the other side of the Capitol.

Con: They might not be able to handle another Obamacare repeal failure.

Senate Republicans have tried to roll back Obamacare at least nine different ways, and they've failed each time.

Their very public failures have arguably cost them politically by reviving Democrats' and some independents' support for Obamacare. In Virginia's elections this month, health care was the biggest issue by far for Virginia voters. Nearly 4 in 10 said in exit polls that health care was the issue that mattered most in deciding how to vote for governor — and of those, 77 percent voted for the Democrat, Ralph Northam. In New Jersey's gubernatorial election, health care wasn't the biggest issue among voters, but of those who said it was, 86 percent voted for the Democrat.

Pro: President Trump supports using the tax bill to undo the individual mandate.

Senate Majority Leader Mitch McConnell (R-Ky.) says Senate Republicans are universally opposed to the individual mandate. So why not get rid of it now? So far, no Senate Republican has drawn a line at the individual mandate.

And they might not, said Alice Rivlin, a health-care policy expert with the Brookings Institution. The requirement that people have health care has long been one of the least popular aspects of Obamacare among Republican politicians and the public. On this, there is agreement among Republican senators. “I don't see any Republicans likely to fall on their swords for the mandate,” she said.

Con: As Republicans found out earlier this year, removing a policy they're all opposed to is easier said than done.

Three Senate Republicans voted against Republicans' best chance at a repeal, which also proposed getting rid of the individual mandate. That's in part because repealing Obamacare's central feature without a replacement could cost millions of people their health insurance and wreck the health-care market, all on Republicans' watch.

Three “no” votes is too many to pass tax reforms. Senate Republicans need at least 50 of their 52 members to pass this tax bill. (Or 51 if Democrat Doug Jones wins Alabama's special election Dec. 12 and is seated in time for a vote.)

Pro: Cutting the individual mandate saves Republicans money so they can cut taxes elsewhere.

It saves an estimated $300 billion because, as The Post's Damian Paletta and Mike DeBonis explain, if people aren't required to have health care, fewer people will, which means fewer people will need federal subsidies to help them pay for their health care.

Republicans plan to use that money to permanently cut the corporate tax rate and double the child tax credit to $2,000, reports The Post's Tory Newmyer in his Finance 202 newsletter.

Con: Count Democrats out.

A couple of red-state Democrats up for reelection next year, like Sen. Joe Manchin III (W.Va.), hadn't ruled out voting for Republicans' tax bill. But undoing a central part of Obamacare basically guarantees that no Democrats will support it, said Paul Ginsburg, a health policy expert with the University of Southern California's Schaeffer-Brookings Initiative. Even Democrats in states that voted for Trump want to keep Obamacare intact.

Plus, this proposal hands Democrats ammunition to claim that Republicans are trying to take away people's health care and give the money to corporations.

Half of Americans oppose the plan Trump and Republicans outlined in September, according to new Washington Post-ABC News polling, because they don't think it will help the middle class more than it will help the wealthy.

Bottom line: Republicans are trying to undo Obamacare and pass a tax bill in one swoop, but with great ambition comes great risk.

It's very possible that the cons outweigh the pros, said the independent analysts who spoke to The Fix. Steve Bell, a former GOP Senate budget aide now with the Bipartisan Policy Center, called repealing the individual mandate a “poison pill.”

“It makes the chances of tax reform 50-50,” he said.

Polling analyst Emily Guskin contributed to this report.