Although the polls show Rick Santorum heading for an easy victory today in Louisiana, a national poll just released by Gallup shows Mitt Romney lengthening his lead over his closest rival, while enjoying a large lead in Wisconsin in advance of the April 3 primary.

Gallup:

Mitt Romney's national support among Republican voters has surged in recent days, coincident with his decisive victory in the Illinois primary and a prominent endorsement from Jeb Bush. Romney's support has increased to 40%, the first time a candidate has reached that level in this campaign, and his lead over Rick Santorum is back into double digits after narrowing to four percentage points on March 20.

The data are based on Gallup Daily tracking from March 18-22, an eventful time in the GOP campaign. On March 20, Romney won the Illinois primary, and he got Bush's endorsement the next day. That same day, a Romney aide hinted the former Massachusetts governor would "reset" his positions for the general election campaign in the same manner a child would shake an "Etch-a-Sketch" toy to clear it, which again raised concerns about Romney's issue consistency.

Romney's current positioning could also be affected by the results of Saturday's Louisiana primary, with polls showing Santorum leading there.

Gallup makes a good point, except wins in AL and MS didn't help Santorum going into the IL primary last Tuesday. It appears that momentum as an offshoot of a primary victory may be subsiding, or at least, less a factor in coming races.

Mewanwhile, Rasmussen has Romney up big in Wisconsin:

Mitt Romney holds a double-digit lead over Rick Santorum in Rasmussen Reports' first look at the Wisconsin Republican Primary race.

A new statewide telephone survey shows that 46% of Likely Republican Primary Voters in Wisconsin favor Romney, while 33% prefer Santorum. Texas Congressman Ron Paul is a distant third with eight percent (8%) of the vote, closely followed by former House Speaker Newt Gingrich at seven percent (7%). One percent (1%) favors some other candidate, and five percent (5%) are undecided. (To see survey question wording, click here.)