The race to find out who will run against Donald Trump begins today.

Even before the results of the first Democratic primary contest in Iowa to choose who will run against Donald Trump, the race has already narrowed down to Bernie Sanders and Joe Biden. The other candidates will need to surprise voters, and do so soundly, in the next candidate debate.

Biden is the moderate candidate. The profile of Democrats who vote for Biden is closer to that of Republicans who vote for Trump in one important respect as it concerns the U.S. cultural war: they are religious. Biden has the vote of Democrats who go to church and therefore, live alongside Trump voters. Furthermore, Biden’s rhetoric and image are more moderate than his Democratic opponent.

Sanders’ advantage is that he is more exciting. If he is less likely to take a voter away from Trump in order to vote for a Democrat, Sanders, on the other hand, can draw more people to the polls and increase Democratic voter turnout. Sanders has been working on making his candidacy viable since 2016 with public support from individuals while avoiding business costs and funding, something which is encouraging to Democratic voters.

The blanket is short in politics.* Biden has one advantage. Sanders has another. It's impossible to say which of those advantages would be more important for a Democrat in overthrowing Trump. In the U.S., it is a fact that the incumbent seeking reelection is always the favorite.

*Editor’s note: This expression is considered a way of saying that in politics, no candidate meets one's every expectation.