A new analysis, published by FiveThirtyEight, shows the congressional map for the 2018 midterm elections has a record-setting pro-GOP bias, which could mean more winning for President Donald Trump and his Republican party.

According to the Cook Political Report’s David Wasserman, things are not looking good for Democrats:

Even if Democrats were to win every single 2018 House and Senate race for seats representing places that Hillary Clinton won or that Trump won by less than 3 percentage points — a pretty good midterm by historical standards — they could still fall short of the House majority and lose five Senate seats.

Wasserman attributes this partially to Republican gerrymandering and Democratic voters’ clustering in urban areas, which he says, “has moved the median House seat well to the right of the nation.”

Timing and a “terrible Senate map” for Democrats are also to blame, he says. While Democrats must defend 25 of their 48 seats in 2018, Republicans have just eight of their 52 seats up for grabs.

Another problem for Democrats that Wasserman points out is Democrats hold far more Republican seats on, what he calls, “borrowed time”: Democrats hold six Senate seats from the 26 Republican-leaning states — all six of which are at risk next year.

This bad news for Democrats goes well beyond 2018, the report says. “[T]here’s a larger, long-term trend at work too — one that should alarm Democrats preoccupied with the future of Congress and the Supreme Court.”

In the last few decades, Democrats have expanded their advantages in California and New York — states with huge urban centers that combined to give Clinton a 6 million vote edge, more than twice her national margin. But those two states elect only 4 percent of the Senate. Meanwhile, Republicans have made huge advances in small rural states — think Arkansas, North and South Dakota, Iowa, Louisiana, Montana and West Virginia — that wield disproportionate power in the upper chamber compared to their populations.

By quantifying the partisan bias of Congress over time, “by measuring the distance between each national presidential result and each year’s presidential result in the median House and Senate seats”, Wasserman shows that today the pro-GOP bias in both the House and Senate are at historic highs. According to the report, the last time the Senate had such a strong Republican bias was in 1913 — the year direct Senate elections were ratified.

While their odds don’t look good, there may still be hope for Democrats in 2018. They did, after all, win back control of both chambers in 2006, despite a GOP bias that year. However, it’s definitely a long-shot, Wasserman says, citing the 2010 scenario in which Democrats were able to obtain 60 senate seats, enabling them to pass Obamacare.

What did it take for the party to be able to obtain 60 seats? The Iraq War, Hurricane Katrina and a stock market crash, which generated a huge backlash against President George W. Bush and Republicans in 2008.

Today, it would take even more cataclysmic events under GOP rule to propel Democrats to a supermajority over the next six years.

While it is still early in the cycle, one Republican Senate seat at risk of being lost to the Democrats is Dean Heller’s Nevada seat.

Elected in 2012 with just 46 percent of the vote, Heller is the only Republican senator up for re-election from a state Clinton won last year. He is being targeted from both the right and left and has even been confronted by President Trump over his unease with the GOP’s Obamacare repeal effort.

Amanda House is Breitbart News’ Deputy Political Editor. You can follow her on Twitter at @AmandaLeeHouse.