Steven Senne, Associated Press
Republican presidential candidate, former Massachusetts Gov. Mitt Romney greets supporters during a campaign stop in Metairie, La., Friday, March 23, 2012.

With so much riding on the outcome of Tuesday's presidential primary in Wisconsin, it's no surprise that Mitt Romney's well-funded campaign is increasingly toying with online advertising in an ongoing search for the most effective ways to spread its message.

Specifically, Team Romney has two TV ads running in Wisconsin (one is pro-Romney, and the other assails Rick Santorum). But as Jeremy Peters wrote Sunday for the New York Times, "both commercials … have gone unseen by many voters — up to one-third of them, by some estimates."

Peters further reported: "Romney’s campaign thinks it has found a way to get its ads in front of the increasing number of voters who are not watching traditional television: Find these people online, and show them the ads there. … The Romney campaign and a team of online behavior analysts have spent 18 months trying to fight television advertising’s law of diminishing returns, sifting through data on the browsing habits of tens of millions of computer users as the campaign builds a richly detailed cache of potential supporters."

MSNBC's political team explained last week why the Wisconsin primary comes at a critical juncture in the race for the GOP presidential nomination: "With Mitt Romney holding a sizable delegate lead and with more prominent Republicans (George H.W. Bush and Marco Rubio) formally endorsing the former Massachusetts governor, Tuesday’s GOP primary in Wisconsin is shaping up to be Rick Santorum’s last chance — in math and perception. If Romney wins Wisconsin (where the winner takes all 42 delegates), Santorum can’t stop him from getting to the magic number of 1,114 delegates, according to our math. … When it comes to perception, Wisconsin is Santorum’s final opportunity to convince Republicans that this race isn’t over, and a win in the Badger State would do the trick."

As of Sunday afternoon, the New York Times' FiveThirtyEight political blog "projects about a 9-point win for (Romney) and gives him an 88 percent chance of victory." But in the same post FiveThirtyEight's Nate Silver also cautioned, "a 9-point polling lead is not completely safe. … (It's) just large enough that some of Mr. Romney’s potential voters might take a win for granted and stay home, which could open the door for Rick Santorum."

The Real Clear Politics rolling, seven-day polling average for Wisconsin's Republican presidential primary pegs Romney at 40 percent, with Santorum running second at 32.5 percent.