The final Des Moines Register poll before Tuesday's Iowa Caucuses shows Mitt Romney with a narrow lead over Ron Paul, and Rick Santorum not far behind in 3rd place.

But the numbers may be misleading. The poll was taken over 4 days and while Romney's support remained steady, Santorum doubled his support in the last two days, showing impressive momentum. On the other hand, Paul's support appears to have plateaued and the final two days of polling show the Texas congressman dropping to third place:

The Des Moines Register's latest Iowa Poll shows a surprise three-way match-up in contention to win the Iowa Republican caucuses: Mitt Romney, Ron Paul and Rick Santorum.

Santorum, who has been largely invisible in the polls throughout the campaign season, is now beating the other evangelical choices and has a clear shot at victory Tuesday night.

But political analysts note there's little time for Santorum to cash in and regroup before New Hampshire, where voters weigh in nine days from now, while Romney is positioned to replicate what he's done in Iowa in all the early states.

In four days of polling, Romney leads at 24 percent, Paul has 22 percent and Rick Santorum, 15 percent.

But if the final two days of polling stand alone, the order reshuffles: Santorum elbows out Paul for second.

"Few saw this bombshell coming," GOP strategist David Polyansky said. "In an already unpredictable race this is another stunning turn of political fortune."

What makes Santorum's growth spurt particularly striking is his last-second rise: He averaged 10 points after the first two nights of polling, but doubled that during the second two nights. Looking just at the final day of polling, he was just one point down from Romney's 23 percent on Friday.

This has all the earmarks of an upset. A surging candidate coming on like gangbusters in the final hours, while other major candidates remain stagnant or even lose a little support. Even if Santorum doesn't pull off the upset win, it is likely that his candidacy will receive the most momentum coming out of Iowa if his poll numbers hold up and he finishes second or third.

As for the second tier, Gingrich has disappeared, polling only 12% while Rick Perry's courting of the religious right has helped him slightly. The Texas governor has climbed 5% since the last Register poll but is still mired at 11%. Michele Bachmann brings up the rear at 7%.

One more interesting tidbit from the poll:

Still, the race is fluid, as 41 percent have a first choice but said they could still be persuaded to support another candidate. Fifty-one percent said their minds are made up.