Recent Presidential Election Trends

On the election results page for each state, metro area and county (and each municipality for which election data is available), there is a table with the title of "Recent Trends" that documents the change in vote margin for both major parties, along with that change expressed in percentage terms which is also known as the "Swing Percentage". These are ways of measuring the extent to which an area has changed over the past few years, and gives an indication as to what might happen in upcoming elections.

We will use the data from Fauquier County, Virginia as an example to explain what the numbers in the Recent Trends table mean. Here is an extract from the Fauquier County election results page, displaying the Recent Trends table and the detailed results of the last four Presidential elections for that county.

Presidential Election Results for Fauquier County, VA back to 1900

Click on the Year to view county-level data for that election.

YearTurnout WinnerRunner-Up OtherTotal Votes Diff
2020 83% Donald Trump* (R) 25,106 57.5% Joe Biden (D) 17,565 40.2% 990 [+] 2.3% 43,661 14 11 0.98%
2016 72% Donald Trump (R) 22,127 59.1% Hillary Clinton (D) 12,971 34.6% 2,362 [+] 6.3% 37,460 15 13 0.94%
2012 71% Mitt Romney (R) 21,034 59.2% Barack Obama* (D) 13,965 39.3% 556 [+] 1.6% 35,555 12 12 0.92%
2008 73% John McCain (R) 19,227 56.2% Barack Obama (D) 14,616 42.7% 376 [+] 1.1% 34,219 10 11 0.92%

Click on the Year to view county-level data for that election.

2020 President, Fauquier County, VA
Joe Biden (D) 17,565 40.2%
Donald Trump* (R) 25,106 57.5%
Jo Jorgensen (Lbt) 777 1.8%
Other 213 0.5%
TOTAL 43,661
Turnout: 83% Diff (St): 14 Diff (US): 11

2016 President, Fauquier County, VA
Hillary Clinton (D) 12,971 34.6%
Donald Trump (R) 22,127 59.1%
Gary Johnson (Lbt) 1,191 3.2%
Jill Stein (Grn) 267 0.7%
Evan McMullin (I) 597 1.6%
Other 307 0.8%
TOTAL 37,460
Turnout: 72% Diff (St): 15 Diff (US): 13

2012 President, Fauquier County, VA
Barack Obama* (D) 13,965 39.3%
Mitt Romney (R) 21,034 59.2%
Gary Johnson (Lbt) 323 0.9%
Other 233 0.7%
TOTAL 35,555
Turnout: 71% Diff (St): 12 Diff (US): 12

2008 President, Fauquier County, VA
Barack Obama (D) 14,616 42.7%
John McCain (R) 19,227 56.2%
Ralph Nader (I) 106 0.3%
Bob Barr (Lbt) 98 0.3%
Other 172 0.5%
TOTAL 34,219
Turnout: 73% Diff (St): 10 Diff (US): 11

Comparing the 2020 election results to those from 2016, Donald Trump defeated Joe Biden but with a smaller margin and a lower percentage of the votes than the margin and percentage he attained in defeating Hillary Clinton in 2016. The margin of victory in 2016 was 9,156 votes (22,127 minus 12,971) whereas in 2020 it was 7,541 votes (25,106 minus 17,565).

The second column of the Recent Trends table illustrates this by showing the difference in the number of votes received by both party's candidates. Trump gained 2,979 votes from 2016 to 2020; Biden gained 4,594 votes from Clinton's 2016 total here. The result was a net gain of 1,615 votes (4,594 minus 2,979) for the Democrats, as seen in the third column in the table which is labeled "Δ Margin" (read as "Change in Margin").

In percentage terms ("Swing %") the net gain of 1,615 votes for the Democrats in 2020 is expressed as D + 8.4% in the fourth column of the Recent Trends table. Looking at the raw data from 2020 and 2016, in 2016 Trump won over Clinton by 24.5% (59.1% minus 34.6%). In 2020 Trump's percentage margin over Biden was reduced to 17.3% (57.5% minus 40.2%). The "swing" therefore could be computed as 7.2% (24.5% minus 17.3%).

However the Swing Percentage as shown in the table is not 7.2%, it is 8.4%. Why? Because a slightly different formula is used, one which focuses solely on the share of the vote won by the Republican and the Democrat candidates (i.e. the two-party vote), and excludes all other candidates.

An example of the computation we use to determine Swing Percentage is as follows:

2020 "two-party vote" percentages: Trump 58.8%, Biden 41.2%   (17.6% margin for Trump)
2016 "two-party vote" percentages: Trump 63.0%, Clinton 37.0%   (26.0% margin for Trump).

Therefore the Swing Percentage shown in the table is 8.4%, which is 26.0% minus 17.6%.

Comparing 2020 with 2012, we see that Trump's margin over Biden was nearly identical (in terms of votes) to Mitt Romney's margin over Barack Obama. Trump in 2020 improved on Romney's margin by a net 472 votes. Despite that improvement in votes, the Swing Percentage actually moved to the left when comparing 2020 with 2012. How is that possible? We've already noted that Trump's share of the two-party vote in 2020 was 58.8% which resulted in a 17.6% win over Biden. In 2012 Romney's share of the two-party vote was 60.1% which resulted in a 20.2% win over Obama.

Since Trump's percentage margin of victory (17.6%) was less than Romney's (20.2%), the Swing Percentage is shown in the table as moving 2.5% to the left.

Comparing 2020 to 2008, as is done in the third row of the Recent Trends table, we can see that Fauquier County has moved (swung) to the right overall by about 4 percent, though the swings between consecutive elections have varied considerably.

The last row of the table compares 2016 with 2008. This comparison may be of particular interest given the similarities between those years:

In both cases the incumbent President was ineligible to run again; 2008 featured a Democrat candidate who had a cult following and the full, adoring support of the "mainstream" media; 2016 featured a Republican candidate who had a cult following -- but with the rabid hostility of the so-called mainstream media, along with extensive opposition by politicians, fundraisers and unelected bureaucrats of both parties.