In 2012 each Republican candidate seemed to have his or her 15 minutes (or days) of fame, rising to the top of the polls and then crashing and burning. Since his performance at the Iowa Freedom Summit. Wisconsin Gov. Scott Walker has surged in the polls and gotten substantial media attention. Is he a flash in the pan or the real deal?

One indication of his staying power is his ability to raise money and get risk-averse, competence-focused donors on his side. That seems to be happening in New Jersey Gov. Chris Christie’s backyard. The Wall Street Journal reports: “Several GOP fundraisers from the financial-services industry and other Manhattan business sectors are hosting donor events for Mr. Walker, a likely presidential candidate, when he visits New York next week. The events show that while former Florida Gov. Jeb Bush and New Jersey Gov. Chris Christie have strong support in New York money circles, neither has a lock on the city’s big-dollar donors.” The report continues, “Several fundraisers who backed GOP nominee Mitt Romney in 2012 are now helping Mr. Walker, who is best known for challenging Wisconsin public-sector unions and winning three statewide elections in a presidential swing state.” This strongly suggests that Walker is displacing Christie — whose problems keep multiplying — in the top tier of candidates. (Christie’s approval in New Jersey is now at an all-time low.)

The collapse of Christie and Walker’s rise, if not a cause and effect, are at the very least simultaneous phenomena. For example, in the latest poll in Iowa, Walker is at 16 percent, Christie at 6 percent. In New Hampshire, Walker is at 12 percent and Christie at 9 percent, while in Virginia, Walker is a 16 percent, Christie at 10 percent. A few months ago, Walker barely registered in the polls.

It makes sense that as Walker proves himself to be an impressive conservative with sufficient rhetorical skills to command a big stage, he will gather voters and donors who may have supported Christie but now have qualms about him. Walker seems, for now, able to attract a good deal of establishment support without much effort. If he can attract support from the base and also moderate Republicans, he will be a more versatile candidate than Christie, and a challenge for Jeb Bush.

Walker’s own challenges are three-fold.

First, as he rises in the polls and collect more donors, scrutiny from opponents and the media will increase. He’s a tough politician who survived three elections in four years, but he will need to be up to speed more quickly than he might have expected on a range of issues from immigration to foreign policy to tax reform. Suddenly, a lot of people will press him for his position on X, and he’ll need to have one. The media will revisit the state “ethics” inquiry, although it has been batted down repeatedly and no action initiated against him. Walker should be prepared for the onslaught.

Second, he is going to face pressure from Sen. Marco Rubio (Fla.) on foreign policy, where Rubio is performing impressively on everything from the Israeli prime minister’s speech to Congress to the war resolution against the Islamic State to Ukraine. I tend to agree with David Brooks who finds Rubio at this stage “the most intellectually creative” of the 2016 contenders. Walker has talked about big and bold ideas and will need to begin introducing them.

And finally, Walker will have to resist the pull from the right to define himself in ways that make him less attractive to other segments of the party and to a general electorate. He has attained his current position in the field precisely because he is a tough-as-nails conservative who nevertheless can appeal to a bluish state like Wisconsin. He’ll need to stand his ground, right in the middle of the party as a potentially unifying figure.

In short, Walker certainly is for real. He’s made the jump from  “also running” to top tier competitor. But as the saying goes, this is not even the end of the beginning of the race.