Mr. Romney Has a Narrow But Solid Lead in Michigan, Large and Uncertain Lead in Arizona

Quantitative Analysis from Nate Silver Points to a Good Tuesday for Mitt

[Update:  New polls have caused Mr. Silver’s mathematical models to rate the Michigan race more of a toss up.

Since we ran the Michigan numbers early Monday morning, three new polls are out that make the state look more like a true toss-up and less like one that favors Mr. Romney.

Two of the surveys, from Mitchell Research and American Research Group, in fact give Rick Santorum a nominal lead in Michigan, by 2 and 1 percentage points respectively. The third, from Rasmussen Reports, gives Mr. Romney a 2-point advantage.

We also added a hard-to-track down survey from Baydoun Consulting, which gave Mr. Romney an 8-point advantage. However, it is less recent than the others, having been conducted on Thursday night rather than over the weekend.

Here is the way the race looks at midday Monday before the primary. 

Michigan	VOTE  PROJECTION	CHANCE  OF WIN
Mitt Romney	38.8%	64%
Rick Santorum	36.7	36
Ron Paul	13.2	0

Getting that sweaty feeling yet Mr. Romney?  You should.]

This Forum has often lauded the analytical abilities of Five Thirty Eight’s premier political analyst Nate Silver, for the simple reason that he is the most accurate forecaster of election results.  Mr. Silver uses quantitative models of polling and other data to forecast the percentage a candidate will get and the probability that the candidate will win.

Because the models used by Mr. Silver rely on data as it becomes available, they are not good predictors until just before an election.  So now we have the best forecast available for the Republican primaries in Michigan and Arizona, a day before the election.  The expectation is that Mr. Romney will win Michigan by about 4 points.

Michigan	VOTE  PROJECTION	CHANCE  OF WIN
Mitt Romney	38.9%	77%
Rick Santorum	34.6	23
Ron Paul	15.6	0

The new polls, from Public Policy Polling and We Ask America, gave Mr. Romney leads of two and four percentage points, respectively, over Rick Santorum. They join two other polls released after Wednesday’s Republican debate, from Mitchell Research and Rasmussen Reports, that gave Mr. Romney leads of two points and six points, respectively.

There is less probability of an election night surprise when the polls are fairly consistent with one another, as they are in this case. That’s why our model makes Mr. Romney a 77 percent favorite to win Michigan even though he has a relatively tenuous 4-point advantage there.

A key factor to look at in Michigan will be turnout.  If turnout is down substantially from 2008 this will be an indication of trouble for Mr. Romney in the general election.  Most analysts ignore turnout because it is not an interesting subject, but here it is an important one.

In Arizona Mr. Romney has a large lead for a number of reasons.  One is that Mr. Santorum has not spent much time in the state.  Another is that Mr. Romney’s anti-immigrant image plays well with the anti-immigrant fervor of the Conservative base in that state and now the state’s radically Conservative, anti-Obama Governor has endorsed him.  Look for Mr. Romney to win the state, but it may be closer than Mr. Silver’s models, which do not have the benefit of recent polling.

Arizona	VOTE  PROJECTION	CHANCE  OF WIN
Mitt Romney	43.4%	99%
Rick Santorum	27.1	1
Newt Gingrich	19.3	0

Two Romney wins will set the stage for an interesting Super Tuesday next week.  In those contests the geography is more favorable to Mr. Santorum, but Mr. Romney’s momentum with two wins in Arizona and Michigan may offset that.  Who knows, which is why they have elections.