“Iowa doesn’t pick nominees,” Jonathan Bernstein wrote at Bloomberg View yesterday. “It eliminates candidates.”

Despite everything that makes this year’s contest to succeed Barack Obama so unusual — a septuagenarian self-described socialist challenging a former secretary of state in the Democratic Party, the absence of an establishment consensus in the Republican Party, “super PACs” spending unlimited amounts of money on nominally independent campaigns, Donald Trump — the first voting state still did what it was supposed to do: winnow out unelectable candidates.

Kentucky senator Rand Paul was the last to drop out of the Republican contest on Wednesday. Rick Santorum, a former senator, canceled events in South Carolina, the third voting state, the same day, suggesting that he too might end his campaign soon.

Neither Paul nor Santorum did well on Monday and both were always too far outside the mainstream of their party to win the nomination, let alone the presidency.

Mike Huckabee, another Republican candidate, and Martin O’Malley, a Democrat, both suspended their campaigns on Tuesday already after placing in the single digits in Iowa.

What’s next?

Some of the other low-polling Republican candidates, like retired neurosurgeon Ben Carson and businesswoman Carly Fiorina, may wait until after New Hampshire has voted next week before dropping out.

So may one or two of the moderately conservative candidates who are hoping for a boost in the second voting state. If either Chris Christie, the governor of New Jersey, and John Kasich, the governor of Ohio, doesn’t do well in New Hampshire — a state that is far more similar to their own than Iowa — there wouldn’t be much point for them to stay in the race.

Jeb Bush, the former Florida governor, could stick around longer even if he doesn’t best Marco Rubio in New Hampshire.

Rubio placed third in Iowa and is seen as someone who could unite the more centrist, pro-business wing of the party and the hard-right “Tea Party” conservatives who helped elect him to the Senate in 2010.

Unlike Rubio, however, Bush has a campaign infrastructure in place well beyond the first voting states and a wealthy super PAC supporting his candidacy. Both men have good reason to wait until March, when many Southern states, including Florida, vote, before seeing which one of them has the best chance of defeating Ted Cruz and Donald Trump, now the frontrunners.