Wisconsin governor Scott Walker joined the growing chorus of Republicans urging Mitt Romney to take a more forceful stand, saying the presumptive Republican nominee's campaign has been overly cautious.

The Romney campaign's two-pronged strategy has largely entailed a relentless focus on the economy and a steady indictment of President Obama's record. But in emphasizing Obama's shortcomings, Romney has often failed to articulate the policies he would pursue instead. 

Walker questioned that strategy during an appearance on MSNBC's Morning Joe, saying Romney cannot rely on opposition to Obama if he wants to get voters to the polls.

I think the mistake that they've made is the feeling like it can just be a referendum on the president, the Wisconsin Republican said. It's certainly a part of it for any incumbent, it's got to be a referendum on, do you like or dislike, not just the president, but his policies.

In many ways they've pulled [Romney] back and just want it to be a referendum on the president, Walker added. I don't think that's enough.

Romney's most recent foreign policy speech provides a good example. Romney has regularly depicted Obama as inept and indecisive when dealing with other nations, and this speech was no different. He lambasted the president for naively pursuing a reset in relations with Russia, for dealing too leniently with Iran and for prematurely moving to withdraw combat troops from Afghanistan.

But the likely Republican nominee offered few prescriptions to differentiate his own stance, following a trend. He regularly attacks Obama for not imposing crippling sanctions on Iran and for hesitating to advocate a military strike, despite the fact that Obama has always remained open to a military operation and has presided over sanctions that are undercutting the Iranian economy, and has pledged to do the opposite of Obama on Israel without offering specifics.

Obama campaign press secretary Ben LaBolt dismissed the speech as all bluster, offering no specific plans for our relations with any region of the world. But as Walker's warning demonstrates, it is not just Democrats who are faulting Romney for staying on the defensive.

A recent broadside from the Wall Street Journal editorial board, typically an arbiter of conservative thought, blasted Romney surrogates for saying the Affordable Care Act imposed a penalty, not a tax -- a position Romney later reversed -- and said his campaign erred in assuming it could play it safe and coast to the White House.

The biography that voters care about is their own, and they want to know how a candidate is going to improve their future, the editorial read. That means offering a larger economic narrative and vision than Mr. Romney has so far provided.

The Republican presidential primaries seemed to affirm the Romney campaign's strategy. Voters who prioritized candidates who shared their values or were true conservatives gravitated towards other options, but Romney was able to clinch the nomination in large part by carrying the plurality of voters who wanted the candidate most capable of defeating Obama.

Walker's comments aside, Republican leadership -- or at least  Speaker of the House John Boehner -- seems to have accepted that scenario.

The American people probably aren't going to fall in love with Mitt Romney, Boehner told a voter at a campaign stop. I'll tell you this: 95 percent of the people that show up to vote in November are going to show up in that voting booth, and they are going to vote for or against Barack Obama.