Updated

Rick Santorum has surged nationally in the race for the 2012 Republican nomination after his three-state sweep this week, while Mitt Romney has lost ground among GOP primary voters. In addition, most GOP voters say the nomination race isn’t over -- someone other than Romney could still win. That’s according to a Fox News poll released Friday.

The new poll was conducted over four nights this week -- Monday through Thursday -- so it provides a unique opportunity to compare Santorum’s support before and after his wins in Colorado, Minnesota and Missouri. And the results are striking.

Click here to view full Fox News poll results. 

In interviews conducted on Monday and Tuesday nights -- immediately before the news of his victories -- Santorum received the backing of 17 percent of GOP primary voters. That was well behind Romney (35 percent) and Newt Gingrich (26 percent), and slightly ahead of Ron Paul (14 percent).

In interviews conducted on Wednesday and Thursday nights -- after his wins -- Santorum’s support nearly doubled, which put him tied at the top with Romney for those two days at 30 percent. That’s an increase of 13 percentage points. Over the last two nights, Romney also received 30 percent, a drop of 5 points. Gingrich came in at 16 percent, down 10 points. Paul’s support held steady at 15 percent.

Looking at the results from all four nights of this week’s interviewing, Romney retains his frontrunner spot with 33 percent, followed by Santorum at 23 percent, Gingrich at 22 percent and Paul at 15 percent.

The previous Fox News poll was conducted in mid-January, and since then Rick Perry and Jon Huntsman dropped out of the race. Romney’s support is down 7 percentage points since the January poll, while Santorum is up 8 points, Gingrich is up 8 points and Paul is up 2 points.

For the four nights of polling, voters who are part of the Tea Party movement back Gingrich (34 percent) over Santorum (28 percent) and Romney (25 percent). Paul receives the support of 9 percent of Tea Partiers. White evangelical Christians break for Santorum (31 percent) over Romney (24 percent) and Gingrich (23 percent).

Most GOP primary voters -- 80 percent -- think someone other than frequent frontrunner Romney could still win the Republican nomination, and over half say it’s too soon for any of the current contenders to drop out (54 percent). Moreover, nearly half would still like to see someone else jump in the race (49 percent).

Forty-eight percent of GOP primary voters are satisfied with their field of candidates. That’s far fewer than the 81 percent of Democratic voters who are happy with Barack Obama as their nominee.

Romney (32 percent) and Gingrich (25 percent) are most likely to be seen as the Republicans who make the “best case” against Obama. Santorum (13 percent) and Paul (11 percent) trail on this measure.

Santorum (36 percent) is seen by GOP primary voters as the candidate most “in touch” with everyday Americans. That’s more than twice as many as any other Republican contender: Paul (16 percent), Romney (16 percent) and Gingrich (12 percent). Eight percent say none of the Republican candidates are in touch with voters.

The poll asked GOP primary voters about their conversations with friends and neighbors and the “first thing” that comes up about the candidates. For Romney, it’s that “he’s extremely wealthy” (21 percent), followed by his business background (14 percent), and that he’s a “flip-flopper” (13 percent). Fewer say it’s that he’s Mormon (11 percent) or that he’s the most electable (11 percent).

When talking about Gingrich, the first thing that comes up in conversation is that he’s been married multiple times (17 percent), that “he has big, sometimes unrealistic ideas” (14 percent), and he was speaker of the House (14 percent). Smaller percentages say the first thing is Gingrich’s consulting work for Fannie & Freddie (9 percent) or his debate skills (9 percent).

By a 50-35 percent margin, voters overall say a Washington outsider could do a better job than an insider of making things work in Washington. Among Republican primary voters, the preference for an outsider is even greater -- 59-28 percent.

GOP primary voters are about ten times more likely to describe former Speaker Gingrich as a Washington insider than any of the other Republican contenders. And who is seen as a political outsider? Some 25 percent say Romney and 14 percent say Santorum. Topping the outsider list is Paul -- who has served for more than two decades in Congress -- at 30 percent.

The Fox News poll is based on landline and cell phone interviews with 1,110 randomly-chosen registered voters nationwide and was conducted under the joint direction of Anderson Robbins Research (D) and Shaw & Company Research (R) from February 6 to February 9. For the total sample, it has a margin of sampling error of plus or minus 3 percentage points. For the subgroup of 407 GOP primary voters (242 interviews were conducted in the first two nights of interviewing and 165 were conducted the second two nights) it is plus or minus 5 percentage points.