The last few weeks have had an insane amount of breaking news and "October Surprises." One of the most significant stories of the last several weeks, though, has been all but forgotten in the days leading up to the election: Donald Trump's preemptive refusal to concede gracefully in the event that he loses to Hillary Clinton. Fortunately for Clinton supporters, Clinton could become president without Trump's concession.
During the third presidential debate, Trump declined to say he would commit to, as moderator Chris Wallace called it, a "peaceful transition of power" in the event he lost the presidential election. When asked about the issue, he said "I'll keep you in suspense." The response set off several alarm bells and concerns Trump wouldn't concede even if he lost. However, that shouldn't be an impossible roadblock for CLinton.
Many states have laws triggering official recounts if the margin of victory is small enough, but once the votes have all been determinatively counted, the election is out of the hands of either candidate. A few weeks after the election, electors record their votes in their states' capitals and the candidate who receives at least 270 electoral votes (as determined by the election held Tuesday) wins.
There are some exceptions to this process, though none of them involve an election being suspended purely because of a candidate's refusal to concede. The infamous Florida recount of 2000, for example, was stemmed from the narrowness of the outcome of the voting results. Trump's well-established penchant for suing or threatening to sue people, places, and things suggests that he might try legal recourse to see if he can persuade the courts to prevent her from winning, but such a challenge is unlikely to succeed.
The biggest threat to a Clinton presidency (if she wins 270 electoral votes) is not Trump's refusal to concede but faithless electors. That is, electors are not required to vote for their state's winner — some states have created laws requiring this, but many haven't — so in some states, an elector could theoretically refuse to cast his or her ballot for Clinton.
Two Bernie Sanders supporters in Washington state have indicated that they may not cast their Electoral College votes for Clinton even if she wins the state. If they and enough others carry out their threats, these so-called "faithless electors," who are not elected by the public but are given the ability to affect the election, could prevent a Clinton win. Two Republican electors have reportedly made similar threats about Donald Trump; the four men would join the ranks of 157 faithless electors from previous elections.
Faithless electors are more of a threat to a post-Election Day Clinton presidency than a pouting Trump, but his supporters could still damage her administration in subtler ways. Trump is, after all, an expert in discrediting candidates who are unpopular with the right — he fostered the birtherism controversy that convinced many Americans that President Obama wasn't born in the United States. An equivalent refusal to accept the authority of a President Clinton would damage her credibility (however meaningless his allegations of rigging were) and distract from important issues.
Trump, ultimately, could cause a lot of trouble for Clinton if he lost, but he couldn't prevent her from taking office.