TPM

The 2012 presidential campaign has been premised on the notion that voters faced the greatest choice in a generation. Vastly different candidates, enormous consequences.

The premise took hold in large part because Republicans spent 2011 and 2012 building party- and movement-wide support for a policy platform -- Paul Ryan's budget -- that called for a radical restructuring of Medicare, and deep cuts to nearly all of the government's domestic functions, to finance much lower taxes on wealthy Americans.

But that agenda seemed politically viable because for most of the race (and for good reason) because the conventional wisdom held that if Romney won, it would be on a Republican wave sizable enough to sweep the party into control of the Senate.

That conventional wisdom has recently fallen apart. Today, all major polling aggregators forecast that Democrats will keep a majority of the Senate no matter who wins the presidency. And that's badly damaged the GOP's hope of making sweeping policy changes.

Going into 2012, Republicans were well positioned to take back the Senate. They needed four net seats, or three net seats, plus the presidency, to win control of the upper chamber, and they had opportunities everywhere: Ohio, Wisconsin, Montana, North Dakota, New Mexico, Pennsylvania, Nebraska, Florida, Missouri, Virginia. The Democrats, by contrast, had maybe two possible pickups -- Maine and Massachusetts -- but for the most part their top priority was holding the line against a Republican onslaught.

Today the map looks much different. Republicans are trailing in nearly all of their pickup states (save North Dakota and Nebraska). Democrats have over-performed in Massachusetts and Maine. And weak GOP candidates in Indiana and Arizona have put two very unexpected red states into play.

The TPM Polltracker currently forecasts Democrats losing one seat on November 6. That's consistent with other polling aggregators. Real Clear Politics also puts the race at 52-48. Nate Silver's forecast suggests there's a decent, though slim chance that Dems will either hold the line entirely or even pickup a seat or two.

Either way, it's a devastating forecast for the GOP -- for the party's governing and electoral strategies, but also for its forward-looking agenda.

Without a Senate majority, Republicans can't control the budget process. Which means they can't cram their entire agenda into a reconciliation bill that's immune from the filibuster. It means that even if they force votes on repealing the Affordable Care Act, they'll need 60 votes -- or about a dozen Democratic defectors. Not likely. President Romney would have to stymie implementation of the law from within the executive branch -- a difficult task -- and his tax agenda would be a non-starter. So would his plans for Medicare and Medicaid. He'd still be able to appoint Supreme Court justices and lower court judges, but Democrats would be able to block conservatives they deemed too objectionable.

In other words, if the Senate math holds, this election has transitioned from one of great consequence, and great potential for the conservative agenda, into something altogether different. Well, at least until 2014.