Make a list of the points you are going to cover in your letter of support. Jot down things such as how long you have known the candidate and in what capacity. Number the items from most to least important.
Use the block format. The Writing Center at the University of Wisconsin recommends this format because it is easy to use as all the text starts flush left. The parts of a businesses letter are the return address, date, inside address (the same as the one on the envelope), salutation, body of the letter, closing and signature. Leave a blank line to separate each part of the letter, except between the closing and the signature. Leave three or four lines between those.
Aim for a one-page letter of support, as few people want to read 10 pages of text. Type in your return address or use letterhead. Leave a line and enter the date. Leave another line and add the return address.
Check with the campaign to see if they want the letter written directly to the candidate. If so it would be "Dear Samuel Jones:". If they prefer the letter in the third person, write "To Whom It May Concern:".
Maintain a professional tone in the letter of support at all times. Remember that you don't know where the information may end up, so you want to endorse the candidacy without sounding too gushy. Colorado State University suggests that you write as through you were speaking to someone.
Be direct. Get straight to the point and say, "I am writing to support Jane Smith's candidacy for mayor of Evansville." In the rest of the introductory paragraph, quickly sketch in the points you will cover in the body of your letter and why you are qualified to endorse the candidate.
Mention the candidate's desirable traits and then support them with an example. Instead of writing that James Henry is "community-minded," write "Mr. Henry is community-minded. After the blizzard last February he checked on the seniors on our street and helped them clear the snow from their sidewalks and driveways."
Remember to change paragraphs when you change ideas. Consult your list from step one and work through the points in terms of importance. In the concluding paragraph of your letter, summarize the points you have raised and link it back to your opening sentence. Specify if people can contact you if they want additional information and include your phone number.
End the support letter with "Sincerely," or "Sincerely yours," followed by a comma. This closing is consistent with the formal tone of the support letter. Leave three or four lines for your signature and then type your name.
Leave the letter of support overnight. Read it aloud and put yourself in the reader's place. Correct any grammatical or typographical errors and print a final copy of the letter of support for mailing.