The venerable Des Moines Register Iowa Poll is out, and it shows three candidates bunched tightly at the top of the pack: Mitt Romney in the lead for the first time in the Iowa Poll, Ron Paul in second, and Rick Santorum moving on up fast.

Mitt Romney tops the latest Des Moines Register Iowa Poll in the closing days before the Iowa caucuses, but Ron Paul and Rick Santorum are poised within striking distance.

The poll, conducted Tuesday through Friday, shows support at 24 percent for Romney, the former governor of Massachusetts; 22 percent for Paul, a Texas congressman; and 15 percent for the surging Rick Santorum, a former U.S. senator from Pennsylvania.

But the four-day results don't reflect just how quickly momentum is shifting in a race that has remained highly fluid for months. If the final two days of polling are considered separately, Santorum rises to second place, with 21 percent, pushing Paul to third, at 18 percent. Romney remains the same, at 24 percent.

"Momentum's name is Rick Santorum," said the Register's pollster, J. Ann Selzer.

Another sign of the race's volatility: 41 percent of likely caucusgoers say they could still be persuaded to change their minds.

Read the full story at the Register.