Why the next president's first 100 days are already doomed

Republicans can't wait to retake the White House and unleash a bold, new conservative agenda. But even if they can defeat Hillary Clinton, their plans risk being thwarted by a divided Congress, an extended fight over the Supreme Court and key fiscal deadlines that will hit in early 2017.

Donald Trump and Ted Cruz are promising a sea change if elected, while Clinton is framing herself as the continuity candidate who will build on the work President Obama started.

If Republicans can convince the electorate that it's their turn, their ability to do what they want to do will depend in large part on how the Senate turns out, which will depend on the name at the top of the ticket. If Trump or Cruz are the nominee, Democrats think they'll have a chance at winning back control of the Senate, and would no doubt use their majority to stifle any aggressive new agenda.

"With Republicans in disarray and the party flirting with selecting a weak general election nominee, the benefit of the doubt has shifted away from the GOP and to the Democrats," Stuart Rothenberg, a longtime campaign analyst, recently wrote about the Senate contests.

If the Senate flips to the Democrats, a new Republican president will likely find himself stymied by the upper chamber, making it impossible to do things like repealing Obamacare, a goal conservative voters have been craving for years.