One can start at https://fec.gov. Search for a candidate or a committee. There are summaries for receipts and disbursements. You can download the entire file or choose to browse receipts or disbursements.
Browsing produces a filtered view of all available data for the election cycle selected. Initially the data is filtered to show the candidate or committee(s) selected. Additional filters can be added–more candidates, committees, contributors, recipients, cities, and election cycles.
Raw or processed data
Raw or processed data can be selected at the upper left. Raw data is available soon after a report is filed; processed data will appear later. Details of raw or processed data can be displayed for each entry by checking the box at the right of the item. The source of the data is reports filed, which are archived at docquery.fec.gov. Records may be sorted by date or by amount. The source reports may be selected for viewing.
Some reports are marked as “memo items.” For receipts, memo items often reflect duplicate reports. For example, on Sept. 30, 2019 Jerry Reinsdorf, the owner of the Chicago White Sox, contributed $5,600 to Reed Victory Committee. This contribution appears among other contributions to Reed Victory Committee. This contribution also appears as two contributions of $2800 among contributions to Tom Reed for Congress as a memo item. This amount isn’t included in the total there, and this report appears in the summary under Reed Victory Committee but not under Tom Reed for Congress. This is confusing; looking only at fec.gov/data, some contributions may be overlooked.
Contributions made through ACTBLUE or WINRED appear twice, once as a memo item. They are counted once. For disbursements, memo items often document disbursements made with a credit card.
Filters make it convenient to find specific data. Filters can be used to search multiple committees as well as to restrict the display to specific items. For example, adding a filter for disbursements for “legal fees” shows that Tom paid Jones Day more than $6000 to date during the current cycle. Adding time periods or removing the time period filter shows more such disbursements.
An alternate view of the data is at https://docquery.fec.gov. One can search for all the candidates for an office here. docquery.fec.gov and fec.gov/data appear to be equivalent.