Tom C. Korologos is a strategic adviser at DLA Piper, former ambassador to Belgium and deputy assistant in the Richard Nixon White House; Richard V. Allen is senior fellow at the Hoover Institution, was Nixon’s foreign policy coordinator in 1968, served as deputy assistant in the White House in the first Nixon administration and was national security adviser to President Ronald Reagan.

The phrase “desperate times call for desperate measures” is attributed to Hippocrates. Now is the time for the Republican Party to take decisive, perhaps desperate, measures if it is going to survive. Republicans must look past the 2016 presidential election and start planning for the 2018 and 2020 comebacks.

Here is a four-point plan for moving forward:

First, every major indicator and poll shows Hillary Clinton winning the presidency. So be it.

There isn’t a snowball’s chance that Donald Trump will stop his bombast and preening. If he’s in trouble today, just bet that it’s going to be worse tomorrow.

It appears a political landslide will sweep the country. That’s not all bad. The larger the margin, the greater the chances a Clinton administration will overplay its hand, handing Republicans a clear opportunity to repair the damage in 2018 and 2020.

Second, a massive educational program needs to be initiated on how to “split ticket” vote. Staying home is not an option. Turnout for the down-ticket races is key. Trump will drag down the entire ticket, but it is vital that Republicans maintain control of the Senate, if possible, and at the very least, the House.

With a Republican House, attention-getting hearings can be held every week on the inevitable missteps in a Clinton administration. The domestic scene, from the economy to health care to trade to infrastructure, will quickly ripen for congressional oversight.

Meanwhile, Republicans can shift focus to the midterms. Over the past 21 off-year elections, the president’s party has lost an average of 30 House seats and an average of four Senate seats.

We may also reasonably expect many of the 25 nervous and vulnerable Senate Democrats up for election in 2018 to join forces with the GOP on spending and other issues. Targeting and wooing that group should start immediately both in Washington and in their home states.

Third, there will be more than 2,000 presidential appointees, many requiring Senate confirmation — the entire Cabinet and sub-Cabinet, agency heads and commissions. Republicans should pick and choose carefully the most egregious liberals and expose their views.

Pending Supreme Court nominees still require 60 votes for cloture, and although the pressure to confirm nominees will be heavy, it is not unheard of to vote against justices (think about Robert Bork) or to postpone confirmation hearings indefinitely. Sometimes doing nothing in the Senate is doing something.

Fourth, move quickly to clean house at the Republican National Committee and change the primary rules that allowed Trump to win the nomination.

The RNC must share major responsibility for the outcome on Nov. 8. Having allowed Trump to gain the upper hand over a very good crop of Republican candidates would be Exhibit A of its political malpractice.

For the party chairman to declare that the “primary campaign is over” after Indiana (while Ohio Gov. John Kasich and Sen. Ted Cruz of Texas were still in the race) was a major blunder.

Reforms are needed now for the delegate selection process for 2020. All options, including creating superdelegates, finding ways to limit the number of candidates and setting later primary dates, should be on the table.

The RNC also must assume the role of forming a new “tank of thinkers” as it did in 1964 after Barry Goldwater’s landslide loss to Lyndon B. Johnson.

In 1965, congressmen Melvin Laird (Wis.), John Rhodes (Ariz.) and Gerald Ford (Mich.), William J. Baroody Sr. of the American Enterprise Association (now AEI), W. Glenn Campbell of Stanford’s Hoover Institution, and others became the “shepherds” of the rebuilding process.

They headed efforts by a number of accomplished scholars and specialists to develop a programmatic approach, published as “The Republican Papers,” a mainstream conservative guide to action. Celebrated scholars Arthur Burns, Gottfried Haberler, Paul McCracken, Gerhart Niemeyer and others wrote policy papers to guide Republican members of Congress.

There is an urgent need to find and recruit the 2016 version of the 1960s visionaries.

These are indeed “desperate times,” and are reminiscent of the last time “desperate measures” were taken. Republicans won 47 seats in the 1966 elections, including one by George H.W. Bush. Two years later, Richard Nixon won the presidency — after campaigning in 1966, as it happened, in 47 congressional districts.