Mitt Romney campaigns in Pennsylvania on July 17: The Republican nominee is making one last push in the traditionally blue state.

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itt Romney's campaign and affiliated super PACs are going up with new ads in Minnesota, Pennsylvania, Michigan, and New Mexico — all blue-leaning states that have long appeared to be in President Obama's win column. The Romney campaign insists that the push is an extension of the momentum it has built up for the past several weeks, allowing the GOP candidate to expand the electoral map to compete in Obama's strongholds. The Obama campaign says Romney is bluffing big time, and senior adviser David Axelrod has even pledged to shave his distinctive, shaggy-dog mustache of 40 years if Romney takes Minnesota, Michigan, or Pennsylvania. But at least one poll shows that Obama's lead over Romney in Michigan has been shaved to a mere 2.7 points.

Is Romney really on the warpath in blue territory? If he is making a serious push in Pennsylvania and other Rust Belt states, it may mean that "Romney is desperately searching for a last-minute path to the needed 270 Electoral College votes — without all-important Ohio," say Brian Bakst and Thomas Beaumont at The Associated Press. Obama continues to hold a slim but consistent lead there, and without the Buckeye State, Romney's path to the presidency becomes very narrow. In that sense, Romney's foray into other blue states may be the equivalent of a Hail Mary pass.

Alternatively, he could be "trying to keep the momentum storyline going even though momentum is gone," says Amy Walter at ABC News. "As our tracking poll has shown, whatever momentum Romney had last week has stalled. So, what better way to keep the 'momentum' storyline going than to show a campaign confident enough to expand the map"?

Or Romney's efforts could simply reflect the fact that this election is drowning in money, with fewer and fewer places to spend it, says Aaron Blake at The Washington Post:

As viewers in all these swing states can attest, there are only so many political ads you can air in one media market, and many markets are becoming saturated.

In addition, at some point, the law of diminishing returns takes effect. Rather than spend that extra $1 million in expensive areas like Northern Virginia or Columbus only to have it lost in a bevy of campaign ads, why not take a flyer in Minnesota, where polls suggest an upset is possible — if not likely?

So how can we know for sure? This is one of those cases where following the money is a bad idea. Instead, watch the candidate, says Jonathan Martin at Politico:

That’s the real test of how serious Romney’s team is taking Pennsylvania and Minnesota — how they spend their human capital. Will they take their candidate off the Ohio-Virginia-Florida treadmill and drop him into Minnesota or Pennsylvania?

Asked if Romney was going to visit either, [campaign official Rich] Beeson only offered up a "stay tuned."