(CNN) Over the weekend at Camp David, Republican congressional leaders huddled with President Donald Trump to talk about, among other things, the 2018 election.

It was a "constructive" discussion that was "grounded in reality," according to a source familiar with the talks, report my colleagues Phil Mattingly, Jeff Zeleny and David Wright

The reality -- and I'm not sure how much of this was accurately conveyed to Trump -- is that every leading indicator points to a wave headed Republicans' way that could well deliver control of the House to Democrats in 2019.

Here are four numbers that tell the story (with a special thank you to super-lobbyist Bruce Mehlman's always terrific quarterly PowerPoint ):

40: That's the average -- AVERAGE -- seat loss for the president's party in midterm election since 1962 when the president's approval rating is under 50%. Trump's approval rating in the Gallup weekly tracking poll released Monday afternoon? 37%.

That's the average -- AVERAGE -- seat loss for the president's party in midterm election since 1962 when the president's approval rating is under 50%. Trump's approval rating in the Gallup weekly tracking poll released Monday afternoon? 37%. 12: That's the average Democratic lead in the generic congressional ballot as of late December. ("If the election were today, would you vote for a Republican or a Democrat to represent you?") That's worrisome when you compare it to where the generic stood in other major wave elections. At this time in the 2014 election, a very good election for Republicans, Democrats had a nearly 2 point edge on the generic ballot. In 2006, the midterm election where Democrats won back control of Congress, the party's generic ballot edge was only 10 points.

That's the average Democratic lead in the generic congressional ballot as of late December. ("If the election were today, would you vote for a Republican or a Democrat to represent you?") That's worrisome when you compare it to where the generic stood in other major wave elections. At this time in the 2014 election, a very good election for Republicans, Democrats had a nearly 2 point edge on the generic ballot. In 2006, the midterm election where Democrats won back control of Congress, the party's generic ballot edge was only 10 points. 3: There have only been three midterm elections -- 1934, 1998 and 2002 -- in the last century where the president's party didn't lose House seats. In all three of those elections there were major extenuating circumstances -- Great Depression, Clinton impeachment and September 11 terrorist attacks -- that upset the historical trend. Short of that sort of cataclysm, however, the president's party usually gets walloped.

There have only been three midterm elections -- 1934, 1998 and 2002 -- in the last century where the president's party didn't lose House seats. In all three of those elections there were major extenuating circumstances -- Great Depression, Clinton impeachment and September 11 terrorist attacks -- that upset the historical trend. Short of that sort of cataclysm, however, the president's party usually gets walloped. 0: Exactly none of the past five presidents have seen their job approval numbers go up in the year before their first midterm election. (Shout out to Republican pollster Lance Tarrance for this data point!). President Obama went from +13 in approval in 2009 to +1 in 2010. Ronald Reagan went from +18 in 1981 to -3 in 1982. You get the idea. Barring a massive unforeseen event, it's very unlikely Trump's approval rating gets much better between now and November.

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