In 2008, Barack Obama was the overwhelming presidential choice of the millennials — voters who came of age after the turn of the century. He still is, but according to polls conducted by the Harvard University Institute of Politics and others, his numbers are shrinking.

The question is, why?

Those millennials have been joined by a new group of millennials, young voters who were not old enough to vote in 2008. Research indicates these new millennial voters are far more fiscally conservative than the older millennials who supported Obama.

And even some of the older millennials are wavering.

The economy is the key.

Older millennials grew up in prosperous times and entered the job market with high expectations. Those expectations were dashed by the recession, and though they might blame policies of the previous administration for letting the economy go sour, they blame the current administration for not doing anything about it. Though most still favor Obama, that support is not what it used to be.

As for the younger millennials, they grew up watching many of their older counterparts lose their jobs, lose their savings, lose their homes, lose all those things they worked for. Their anxiety level is high and their support for the president is low.

Whether they will vote Republican is a vital part of next week’s election.

They probably would if the election were purely about the economy. However, young millennials are socially liberal (or, at least, more liberal than the GOP presents itself) and while the economy is still their main concern, their hands-off attitude toward social issues like gay marriage and abortion has spilled over into economic attitudes to the point that some are turning to the Libertarian Party.

Worth noting also is that interest in organized religion is also waning among the younger millennials, something that has shown up in polls that have identified what is being called the “nones” — those with no religious affiliation.

All of this has produced a growing number of young people who respond “don’t know” or “don’t care” when asked if they were liberal, conservative or moderate.

Can Obama keep millennials in his camp? Can Republicans capitalize on the dissatisfaction among millennials? (The GOP is trying. Vice presidential candidate Paul Ryan has been stumping on college campuses.) Or will the millennials be so discouraged by both parties that they will either vote Libertarian or stay home?

On the answers to those questions might hang the election’s outcome.