Speaker of the House Tip O’Neill once said, “All politics is local.” That may have been true in Tip O’Neill’s day, but some elections are decisively on national issues — and the Congressional elections this year are overwhelmingly national, just as the elections of 1860 were dominated by one national issue, namely slavery.

In 1860, some abolitionists split the anti-slavery vote by running their own candidate — who had no chance of winning — instead of supporting Abraham Lincoln, who was not pure enough for some abolitionists. Lincoln got just 40 percent of the vote, though that turned out to be enough to win in a crowded field.

But what a gamble with the fate of millions of human beings held as slaves! And for what? Symbolic political purity?

This year as well, there are third-party candidates complicating elections that can decide the fate of this nation for years to come. No candidate that irresponsible deserves any vote. With all the cross-currents of political controversies raging today, what is the overriding national issue that makes this year’s Congressional elections so crucial?

That issue is whether, despite all the lawless edicts of President Barack Obama, threatening one-man rule, we can still salvage enough of the Constitution to remain a free, democratic nation.

Obama will be on his way out in two years, but if he can appoint enough federal judges who share his contempt for the Constitution’s limits on federal government power in general — and presidential powers in particular — then the United States can continue on the path to becoming another banana republic, even after Obama has left the White House. Obama understands how high the stakes are, which is why he is out fundraising all across the country seemingly all the time.

In his vision, our betters in Washington shall simply order us to live as they want us to live — telling us what medical insurance we can have, what doctors we can go to, what political groups shall be favored by the Internal Revenue Service, with more of the same coming in the years ahead, long after Obama has left the White House.

Obama understands clearly that his ability to fundamentally remake what he has long seen as a deeply defective and corrupt America in the image of his far-left vision depends crucially on having control of the Senate that has the power to confirm his appointments of federal judges with lifetime tenure. His fundraising is key to maintaining the Democrats’ Senate majority.

Foreign policy is subordinated to Obama’s overriding ideological vision. The president will not risk losing this year’s Congressional elections by taking military actions that will alienate his political base. Token military actions can minimize the political losses from other voters.

That people will die while he stalls on military action is a price he is willing to pay. His ordering thousands of American troops into Ebola-infested Liberia shows the same ideologically driven callousness.

The big question is whether those who wish to preserve a free America see the issue and the stakes equally as clearly as Obama does — and see that this is the overriding national issue of our time, with our votes for Senators not to be confused by local issues.