Heading into the final weeks of the midterm campaign, the political landscape continues to tilt in favor of the Republican Party, with President Obama’s overall approval rating at the lowest level of his presidency and GOP voters signaling greater likelihood than Democrats that they will cast ballots, according to a new Washington Post-ABC News poll.

Americans are looking to November and beyond with dissatisfaction about the state of the country and the political leadership in Washington. Two-thirds say the country is seriously off-track. And while more than 6 in 10 say the president lacks a clear plan for governing, a slightly higher percentage says the same of Republicans in Congress.

Public impressions of the two political parties are similarly gloomy. “Favorable” ratings for the Democratic Party (39 percent) are at a 30-year low, and for the first time a majority (51 percent) gives the Democrats an “unfavorable” rating. The Republicans are rated even lower, with a 33 percent “favorable” mark. That is little changed since last year’s government shutdown, although the party’s “unfavorable” rating has improved.

Most worrisome for Democrats is that their candidates will be weighed down by unhappiness with the president. Obama’s overall approval rating stands at 40 percent, the lowest recorded in a Post-ABC News poll during his six years in office, though it is only a point lower than last month. Among independents, his rating is 33 percent.

The president’s economic approval rating is better, at 44 percent, and has been moving up over the past year, coinciding with better economic news and a decline in the unemployment rate. Disapproval of his handling of the economy is at 51 percent, the best it has been since September of last year.

View Graphic Little affection for Republicans or Democrats heading into midterms

But public support for his handling of the threats posed by Islamic State extremists has tumbled dramatically in just the past few weeks, falling from 50 percent approval at the end of September to just 35 percent today. Three weeks ago, his rating on dealing with the Islamic State was a net positive by six points. Today it is net negative by 16 points.

On other measures, the president is at or near low points, whether international affairs, terrorism or implementation of the Affordable Care Act.

His worst rating comes on his handling of immigration, with just 29 percent saying they approve of how he has handled the issue, down nine points since June. Obama has said he will use his executive powers to make changes, including giving some kind of legal status to millions of undocumented immigrants — but not until after the elections, a decision that satisfied neither side.

Meanwhile, analysis of the survey findings shows that the Republican electorate is more motivated to vote in this election than are the Democrats. Seventy-seven percent of Republicans say they are certain to vote, compared with 63 percent of Democrats.

Democrats often have more trouble turning out their base voters in midterm elections. This year, they have made unprecedented efforts to register new voters and turn out those who often vote only in presidential races.

Midterm elections generally are a referendum on the party that holds the White House, and the president’s party almost always loses seats. Today, 62 percent of registered voters say the president will not be a factor in their vote next month, up eight points in a month. But among those who say he will be a factor, more say they will use their vote to send a message that they oppose Obama.

Among independents, 23 percent say they want to send a message to oppose the president while 8 percent want to support him with their vote. Meanwhile, 46 percent of Republicans say they will vote to send a message of opposition to the president, while just 30 percent of Democrats say they are voting to send a message of support for Obama.

View Graphic Election Lab: See our current forecast for every congressional race in 2014

Four years ago, when Republicans made major gains, the scales on this question were more evenly balanced. Then, 49 percent of Republicans said they wanted to send a signal of opposition to Obama with their vote, while 50 percent of Democrats said they were sending a message of support.

On the question of which House candidate, Republican or Democrat, people plan to vote for, Democrats hold a tenuous edge of 46 percent to 44 percent among registered voters. But among likely voters, Republicans hold a more sizable advantage, 50 percent to 43 percent. Self-identified independents favor Republicans 51 percent to 32 percent, and among the roughly one-quarter of the likely electorate that has an unfavorable view of both political parties, Republicans hold a lead of 53 percent to 32 percent.

The question has been an imperfect indicator of election results, but generally Democrats need a bigger advantage to do well in elections.

There is no similar question about Senate races. Republicans need to win a net of six seats to take control of that chamber, and they have opportunities in more than enough states to do so. Competitive races in several Republican-held states have complicated the forecasts, although political models give Republicans the edge.

The Democrats do best on questions of which party seems more in touch with average Americans. Pluralities of registered voters see Democrats as better representing their own personal values, as being more concerned about people’s needs and as better understanding the economic problems that people are having. A plurality of registered voters see Republicans as the party with better ideas about the right size and scope for the federal government.

The public is more evenly divided on the question of which party is more trusted dealing with the country’s main problems. Among all adults, whether registered to vote or not, Americans split evenly, 39 percent to 39 percent, with 15 percent saying they trust neither party. (The rest say they trust both parties equally or have no opinion.)

Until this fall, Democrats have long had the advantage on this question among the general population, sometimes by double digits. When the results are limited to registered voters, the survey finds Republicans with a slim three-point advantage, growing to eight points among likely voters.

On specific issues, Democrats lead among registered voters on health care, helping the middle class, abortion, same-sex marriage and, by 27 points, dealing with issues of importance to women. Republicans lead on the economy, the deficit and, by 19 points, dealing with threats from the Islamic State.

Jobs and the economy still top the list of issues voters say are most important in their decision, at 37 percent, with Democrats, Republicans and independents in almost identical agreement. For both Democrats and Republicans, health care ranks second, but independents say the way things are working in Washington is their second-most-important issue.

The Post-ABC poll was conducted by telephone last Thursday through Sunday among a random national sample of 1,006 adults, including interviews on conventional and cellular phones. The overall margin of sampling error is 3.5 percentage points.

Peyton M. Craighill contributed to this report.