In recent decades, Democrats and Republicans in Congress have become increasingly polarized as Democrats have become more liberal and Republicans more conservative. This graph shows the difference between each party's average ideology in each chamber of Congress over time.

Difference between Party Ideology

Which statement is best supported by the data presented in the chart?

Differences in party ideology are always greater in the House than in the Senate.

Differences in party ideology in the House and Senate do not seem correlated or related to each other.

At many points in the history of Congress, there is basically no difference in ideology between the two parties.

After a period of lower differences in party ideology in the middle of the $20$th century, these differences have grown since about $1980.$