Americans voted for Barack Obama in 2008 despite, not because of, his most partisan voting record in the Senate. They were once willing to look past his earlier dubious associations with abject anti-Semites such as the Reverend Jeremiah Wright, former terrorists like Bill Ayers, and unhinged characters such as Father Pfleger. They also averted their eyes from Obama’s often quite offensive commentary, in his autobiography and during the 2008 campaign (e.g., "typical white person" and "they cling to..." speech).
Instead, voters were tired of the Iraq War (which was over for all practical purposes by the time of the November 2008 election).
They were, of course, terrified by the September 2008 financial meltdown (which had been mostly stabilized four months later by the time of the inauguration) and irate at the kid-gloves treatment accorded often conniving banks and investors.
They were convinced that Obama might be healing and transformative as the first African-American president, supposedly only slightly to the left of a far steadier and more qualified Condoleezza Rice or Colin Powell. And half the Democrats were already becoming sick of Hillary Clinton once they became reacquainted with her on the 2008 primary-campaign trail.
As is typical of American politics, voters in 2008 also wanted to change the party in power after it had been in the lead for eight years, and the lame-duck president fell out of favor. Voters certainly were underwhelmed by an uninspiring, herky-jerky, mostly incompetent John McCain campaign, notable for his "that’s not who we are" comments and his willingness to "lose nobly."
Such was the naïve dream.