With the U.S. midterm elections looming, the Republican and Democratic parties are ramping up their advertising campaigns in key races, bolstering their social media presence, targeting voters in person and enlisting prominent politicians to endorse candidates at rallies nationwide.

Despite the domestic challenges facing the United States — persistent inflation, declining stock and bond markets, flat job figures and intense polarization — and the resultant low popularity of President Joe Biden, the midterm elections could be much closer than one might expect.

Given the president’s poor support rates, history suggests the Democrats will struggle in the upcoming elections. Democrats hold a slim majority in the House of Representatives, with a number of candidates under threat in competitive districts. A number of veteran Democratic lawmakers have retired from politics over the past two years, which hurts the party’s chances further. And voters generally tend to punish whichever party is in control of Congress irrespective of the country’s actual position.

Yet the election remains a wildcard. The Democratic Party is favored to hold the Senate on the back of an electoral map that slightly favors the Democrats in terms of contested seats, according to the latest ratings by data organization FiveThirtyEight. And even though the Republicans have a much stronger advantage in the House, FiveThirtyEight says the Democrats have a 30% chance of holding the House despite Biden’s poor support rate.

There are several reasons the Democrats might perform better than expected in the elections. Many Democrats have been galvanized by the Supreme Court’s decision to overturn Roe v. Wade, the GOP has selected some relatively weak candidates in several Senate elections and the Biden administration’s approval ratings have ticked upwards slightly in recent months, probably due to the Ukraine war as well as some mildly improved economic indicators.

The results of the midterm elections could have significant implications for the Asia-Pacific region. In the past, particularly in regard to Southeast Asia, presidential administrations going back to the George W. Bush administration have often ignored important regional issues.

In response, Congress has repeatedly stepped in and involved itself heavily, particularly on issues relating to Myanmar, human rights, U.S. defense spending, the normalization of U.S.-Vietnam ties and other matters. In other words, Congress plays an outsized role in the Asia-Pacific region, often larger than it does in relation to the United States’ allies in Europe and the Middle East.

Were the Democrats to defend control of the House and the Senate, there would be continuity in the administration’s policy on Asia. Of course, there is internal debate even within the Democratic Party about its policy on Asia, but most lawmakers are reluctant to openly criticize their president’s foreign policy.

If the Democrats retained control of Congress, it would likely mean a continued ramping up of an assertive policy on China, both actually in the region and through U.S. industrial policy. As a result, the administration would most likely continue to ignore much of Southeast Asia, including the catastrophic civil war in Myanmar and the state of the Association of Southeast Asian Nations in general.

A Democratic victory in both houses of Congress in the midterm elections would probably lead to a foreign policy focus almost exclusively on Northeast Asia, as well as a very significant effort by the administration to sell its signature Indo-Pacific Economic Framework proposal to partners in the region. The proposal doesn’t appear to contain much of interest to the region and pales in comparison to a genuine trade agreement, but continued Democratic control would almost surely mean pushing the agenda as much as possible.

However, split control of the U.S. government — in which the Democrats control the presidency and the Republicans control one or both houses — could spur changes in the administration’s policy on Asia. As noted, it is unlikely that the Republicans will take the Senate and, even if they did, Republican senators in general — particularly GOP leader Mitch McConnell — tend to be aligned with the Biden administration on policies related to China and Taiwan, as well as an increased emphasis on Northeast Asia and Australia.

However, there are a growing number of Republican senators who lean in a more isolationist direction. Their numbers are rising sharply within the Republican Party, which is becoming more wary of U.S. involvement in many parts of the globe.

If a few more isolationist-leaning GOP senators manage to win seats in the midterm elections, it could lead to more robust debate within the U.S. Congress about its overall defense spending and defense arrangements with Australia, South Korea and Japan, as well as serious debate about whether the U.S. should make a vague commitment to defend Taiwan.

As any party in opposition typically likes to undermine a sitting president, especially in the runup to a presidential election, a GOP Senate would likely criticize the Biden administration’s Asian economic agenda. Although some senators such as McConnell do support engagement with Asia on economic issues, there would be genuine division within the GOP caucus.

In the House, GOP gains in the midterm elections could potentially have even more of an impact on policy toward Asia. There are considerably more isolationist GOP lawmakers in the House already and many more are running for office in November.

If the GOP wins the House, even a House Speaker who was generally internationalist would have to cater to what would probably be an influx of isolationist members who broadly support the policies espoused by former President Donald Trump, who remains one of the most powerful figures in the party and is suspicious of U.S. relationships with many Asian partners, whom he believes do not contribute enough to their own defense.

Facing such pressure, a GOP House speaker might focus on rethinking the U.S.-South Korea relationship and other U.S. treaty alliances in Asia. This could pile pressure on the Biden administration to reaffirm its position on Taiwan, and it seems increasingly clear that Washington would defend the island if it was ever attacked.

However, some — but a growing number — in the GOP might not want to intervene if Taiwan was attacked, and this could become a major bone of contention over the next two years.

Joshua Kurlantzick is senior fellow for Southeast Asia at the Council on Foreign Relations.